During the next year we intend to continue to expand our program in the determination of the thermodynamic properties of the siderophores and model compounds. In particular, we wish to address the question of why we see a large chelate effect in the catecholate-based siderophores and no such effect in the hydroxamate-based siderophores. We also wish to examine the transport properties of chromium-substituted kinetically-inert complexes of desferriferrioxamine B in its producing organism. Studies of the structures and spectroscopic properties of these compounds will also be continued.